The Border Wars.

Since the creation of Edda, the land has been divided by thin magical barriers. Ones that let living things through, but stopped environments from colliding with one another. As such, when kingdoms, countries, and civilizations began to grow and expand, they treated these arcane lines as their pre-made borders.
But that wasn't enough. It never is.
At the time the world consisted of Hippolyta, Agartha, Avalon, Kaguya, Atalanta, and Magnum Opus. Their leaders at the time had grown unimpressed with the predesignated lots of land and wished to expand even further. But, at this time many did not see a need for war, and so they all met under the pretense of a political discussion.
That is when tragedy struck. On the 18th of Drying Summer, 953 AC, the meeting place of the rulers, which should have been a well-kept secret, was destroyed in an explosive act of terrorism. In one fell swoop, the rulers of all Six countries at the time, and swathes of their legislative and judicial cabinets, were turned to ash and black marks against the rubble.
Combined with the shock and outrage, countries and populations pointing fingers at one another, those who would take the reins of control were warmongers, greedy profiteers, and madmen eager to see blood and trample over their enemies.
As soon as provisional leaders were chosen, the wars were declared, and the world dissolved into chaos.
It was a bloody and long 20 years of constant violence and chaos. As victory grasped from each side more and more, drastic measures were taken that violated simple morality. Deaths piled up by the thousands. In the chaos of it all, Laputa, previously a part of Atalanta, and Boncly, previously part of Boncly, used the chaos to stage civil uprisings and seceded from their original owners, adding two more competitors to the war for land and control.
Rulers were assassinated and replaced in days, each one more vitriolic and crazed than the last. While those who worked in combat and war thrived, innocent civilians suffered in droves, with nary a reward in sight. 
On the 14th of Blooming Spring, 973 AC, 19 years into the existence of the war, the first light of peace began to shine.
Several armies from Hippolyta, Agartha, and Atalanta had gathered in Magnum Opus, where Theogony is located now, but were observing a day of a cease-fire to honor the fallen soldiers thus far. But on this day, someone incited another conflict.
No one knows exactly what caused it, but on the supposed day of peace and silence, mass chaos and death erupted in the city, killing as many soldiers as it did civilians in the chaos. But then, something strange happened.
Someone talked.
It was an incredibly mundane thing, but it shook the warring armies. Something compelled them to gaze upon who it was that, in the middle of a deadly massacre of steel and magic, would call for them to stop with words alone.
They gazed upon a young man, seemingly human, with azure robes upon a pile of stone rubble. He had no weapons or defense, and even as he stood with a staff, he tossed that down as well. And he talked. He shouted. He cried.
He called out and chided the soldiers and warriors of the different nations, scolded them for disturbing the day of peace, and scolded them for taking up arms in the first place. He scolded them for following the orders of madmen who sat on gilded thrones while ordering the innocent to die. He explained to them that they were literally spilling their own blood and the blood of innocents, the blood of neighbors, the blood of fellow kinsmen for imaginary lines of land that did nothing but divide where people called home. Homes that they were destroying, homes they were damning, homes that were ruled and mired by fear and hatred. He stood upon a simple pile of stone, with nothing but his words to defend himself from armies of angry soldiers armed to the teeth.
And they listened.
He had not been the first person to call for peace, and he wouldn't be the last. But at that moment, to those soldiers, his words were what they needed to hear. What they wanted to hear. Perhaps there was some underlying magic to that day, maybe the world itself put a spell on the people, as the world cried out for peace. No matter how it happened, on that day, the soldiers listened.
Generals came from their tents and rear lines to listen to this speech being delivered by such a young man, who had captivated their soldiers to a standstill when not a moment prior they were at each other's throats. 
And they listened.
Soldiers and Generals threw down or sheathed their weapons. Healers began to fix what they could. Some still were not convinced, but soldiers and civilians alike formed a wall around the young man as his speech continued, pointing out the crimes each nation had done in turn, that there were no innocent soldiers in this battle until they chose peace and made right their wrongs, and he set forth how they could do just that, how he believed in the power of personal faith and redemption for all.
And they listened.
The war had many conflicts, many infamous events, many deaths, that all ended as statistics or lessons of wrongdoing, but this was the key event in the War. This is what began to end the War. This was The Calming of The Masses, the biggest accomplishment in the life of the man who would become King Baal Theophrastus Diomedes the 3rd, the future king of Magnum Opus. 
Of course, while he gave his speech alone and defenseless, Diomedes was not alone in his thoughts. There were many who believed in peace such as he did, some of them were even the generals who led the armies that threw down their weapons, and as they added more and more tired soldiers to their number, they became an army of their own. They went to the biggest sites of conflict and spread their words, their ideas, and their mission, and one by one the armies became for naught.
On the 30th of Falling Autumn, 974 AC, the newest rulers of the now 8 Countries of the world all agreed to peace, and The Border Wars came to an end. 
Afterward would come The Scarlet Restoration, the legal process that put every soldier on trial. 85% were declared innocent of war crimes, but still required to work with the newly established Recreation Corps as repayment for their sins. 10% were unrepentant and were sentenced to prison, with the hope that they would learn and reform. The final 5% were wholly guilty and contained many of the politicians and former leaders that spurred on the conflict for 20 bloody years. They were executed.
Sadly this would not be the end of conflicts. Four years after The Border Wars, the Kaguyan Civil War flared up as a result of political parties coming into harsh conflict, which split the country into what is now West and East Kaguya, and the scuffles that resulted in Alicein splitting off from Boncly.
Now, in the present day, some peace has finally settled among the land, and while some tensions are still high, and the war caused irreparable damage, many people know to think twice before calling for wars.

Conflict Type

War

Start Date

30th of Falling Autumn, 954 AC

Ending Date

30th of Falling Autumn, 974 AC

Conflict Result

All nations called for a cease-fire, treaties were devised, and the guilty were put to trial.